1. Technical Field
The present invention relates to a sheet sucking/feeding device which sucks an uppermost sheet among a plurality of stacked sheets, and separates this uppermost sheet from another sheet therebeneath, and feeds out the uppermost sheet.
2. Description of the Related Art
A technique in which, by using a printing plate (e.g., a PS plate, a thermal plate, a photopolymer plate) in which a recording layer (photosensitive layer) is provided on a support, an image is recorded directly by a laser beam or the like onto the photosensitive layer of the printing plate, has come to be developed as a printing plate exposing device. With this technique, it is possible to quickly record an image onto a printing plate.
In an automatic printing plate exposing device using the technique of recording images onto printing plates, large numbers of printing plates are stacked and accommodated in cassettes. The image forming surface of the printing plate is easily scratched. In order to protect the image forming surface, protective sheets (interleaf sheets) are superposed on the image forming surfaces of the printing plates. Sets of the superposed printing plate and interleaf sheet are successively stacked in layers within the cassette. When a printing plate is to be removed and fed out, one end portion of the uppermost printing plate among the plural printing plates stacked in the cassette is sucked by suction cups so as to separate this printing plate from the others. The printing plates are thereby taken out one-by-one, and are fed sheet-by-sheet (conveyed and fed) to the subsequent process (e.g., an exposure process) while being inverted.
However, when the printing plates are fed out sheet-by-sheet while being sucked by suction cups and taken out one-by-one and inverted as described above, there are cases in which, due static electricity between or sticking due to a vacuum between the uppermost printing plate which the suction cups are sucking and the next printing plate (the printing plate therebeneath), the next printing plate (the printing plate therebeneath) also is lifted up.
Therefore, conventionally, a “separating plate” has been provided along the locus of movement along which the printing plate is lifted up and raised while being sucked by the suction cups (e.g., in the corner portion of the top end of the cassette) Due to the printing plate passing by the “separating plate” while contacting the “separating plate” or being temporarily stopped while contacting the “separating plate”, the next printing plate (the printing plate therebeneath) is separated therefrom. Refer to Japanese Patent Application Laid-Open (JP-A) Nos. 2002-128297 and 2001-151360.
However, in a method of separating which uses such a “separating plate” (i.e., in a structure in which a “separating plate” is provided at the corner portion of the top end of the cassette for example), this “separating plate” gets in the way at the time when printing plates are loaded into the cassette. The user carries out the operation for inserting and loading the printing plates in while setting the “separating plate” in a withdrawn state (i.e., while keeping the “separating plate” out of the way). This is a cause of deterioration in work efficiency. Further, even if the next printing plate (the printing plate beneath) is separated (disjoined) after passing by the “separating plate” at the time when a printing plate is being removed and fed out from the cassette, that separated next printing plate (the printing plate which was beneath) rides up on the “separating plate”, and there is the possibility that problems in sucking may arise during the next sucking/feeding operation. Moreover, the position at which such a “separating plate” is disposed must be adjusted in accordance with the size of the printing plates. The workability deteriorates for this reason as well.